1. Field of the Invention
The present invention relates to an apparatus for varying the speed of copies, such as signatures or folded flat products, of the kind that are produced and processed in a folding system, for instance.
European Patent EP 0 498 068 B1 relates to a folding system in which the folded copies are transported via a conveyor device, conveyor drums and belts. A high-speed first belt configuration, containing upper and lower belts, is provided, and the folded copy is conveyed between these belts. A conveyor drum configuration that can be driven at variable speed is also provided, with upper and lower conveyor drums which are precisely in phase with one another during their rotation and which engage the folded copy, brought from the first belt configuration, in the region of its leading edge and transported onward. A slow second belt configuration is also provided, which contains upper and lower belts that engage the folded copy, brought from the conveyor drums, by its leading edge and transport it further. The upper and lower conveyor drums have recesses on their circular circumference, and parts of the conveyor drums of large diameter are formed by a rubber coating, and to meter the force between the conveyor drums, at least one shaft is pivotable by control elements.
European Patent EP 0 256 795 B1 discloses an apparatus for processing sheets that includes a device which can receive the sheets, moving at a first speed, and transports them to a conveyor configuration which is driven at a markedly different speed. The device includes a first rotatable drive element for speeding up and slowing down the sheets, so that they can be transferred to the conveyor configuration at the proper speed. The first drive element is driven by a mechanism that includes a planetary gear which includes a sun wheel. A planet wheel is disposed such that in operation it revolves around the sun wheel. A first rotary element is mounted outside the axis of the planet wheel but is rotatably driven by the orbiting planet wheel, and the first drive element is coupled for the revolution by a motion of the first rotary element. The first drive element is supported rotatably on the sun wheel axis and on the other side of the sun wheel. The second drive element is coupled in a manner fixed against relative rotation by one or more second rotary elements, which are disposed such that they execute a rotary motion in the opposite direction from the motion of the first rotary element, or of each first rotary element, as applicable. The second drive element is mechanically coupled with a counterweight, which is provided in order to compensate for changes in inertia that are transmitted to the first drive element. The configuration is such that the drive elements follow a specified speed and acceleration profile, which repeats periodically.
In both of the embodiments disclosed in the above references, uncontrolled braking, a loss of delivery precision, and damage to the folded copies can occur, and this is especially true at high processing speeds and with extremely lightweight printed materials. The limitations described are sometimes made even worse if the folded copies can be grasped simultaneously by two conveyor configurations in conflict with one another, such as one conveyor configuration for higher speeds and another conveyor configuration for lower speeds. The leading-edge region of the folded copy can for instance already have entered the braking device while the trailing region of the folded copy is also being thrust into the braking device by the conveyor configuration for high speeds, which can cause buckling of the folded copy. This is in fact attained in the version according to the European Patent EP 0 498 068 B1 by use of a cyclical variation of the angular speed of conveyor rollers, in order to achieve a continuous deceleration of the folded copy. But the variable speed change causes dynamic and constantly changing stresses on the components, which can impair the mechanical reliability of the component units.